ci: update actions/cache to v4 to fix deprecations

.github/workflows/cygwin.yml

@@ -39,7 +39,7 @@ jobs:
       MESON_CI_JOBNAME: cygwin-${{ matrix.NAME }}
 
     steps:
-      - uses: actions/cache/restore@v3
+      - uses: actions/cache/restore@v4
         id: restore-cache
         with:
           # should use 'pip3 cache dir' to discover this path
@@ -83,7 +83,7 @@ jobs:
           python3 -m pip --disable-pip-version-check install gcovr fastjsonschema pefile pytest pytest-subtests pytest-xdist coverage
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -o igncr -eo pipefail '{0}'
 
-      - uses: actions/cache/save@v3
+      - uses: actions/cache/save@v4
         with:
           # should use 'pip3 cache dir' to discover this path
           path: C:\cygwin\home\runneradmin\.cache\pip

.github/workflows/website.yml

@@ -34,7 +34,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: actions/cache/restore@v3
+      - uses: actions/cache/restore@v4
         id: restore-cache
         with:
           # should use 'pip3 cache dir' to discover this path
@@ -47,7 +47,7 @@ jobs:
           sudo apt-get -y install python3-pip ninja-build libjson-glib-dev
           pip install hotdoc chevron strictyaml
 
-      - uses: actions/cache/save@v3
+      - uses: actions/cache/save@v4
         with:
           # should use 'pip3 cache dir' to discover this path
           path: ~/.cache/pip